USE OF LOW COST RAW MATERIALS IN POROUS SINGLE FIRING PROCESSES

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USE OF LOW COST RAW MATERIALS IN POROUS SINGLE FIRING PROCESSES

F. del Río, V. Beltrán Porcar, J. González Peña, J. Enrique Navarro

To cite this version:

F. del Río, V. Beltrán Porcar, J. González Peña, J. Enrique Navarro. USE OF LOW COST RAW

MATERIALS IN POROUS SINGLE FIRING PROCESSES. Journal de Physique Colloques, 1986, 47

(C1), pp.C1-549-C1-553. �10.1051/jphyscol:1986183�. �jpa-00225614�

USE OF LOW COST RAW MATERIALS I N POROUS SINGLE FIRING PROCESSES

F. SANDOVAL DEL R i O , V. BELTRAN PORCAR* , J.Ma. G O N Z ~ L E Z PEGA and J.E. ENRIQUE NAVARRO*

I n s t i t u t o d e Cerhmica y V i d r i o , C . S . I . C . . Arqanda d e l Rey, Madrid, Spain

" ~ n s t i t u t o d e Quimica TiScnica, Valencia U n i v e r s i t y , D r . Moliner 50, Burjasot-Valencia, Spain

Resum6 - Des compositions de c a r r e a u x de r e v e t m e n t o n t & t 6 f a - briquges p a r c u i s s o n r a p i d e d ' u n e chamotte de c a l c a i r e marneuse espagnole. Les f o r m u l a t i o n s s o n t f a i t e s Zi p a r t i r du diagramme de phase correspondant.

Les v a l e u r s des p r o p r i g t 6 s physiques e t technologiques s e t r o u - v e n t dans l e domaine e x i g e pour c e t y p e de matgriaux. La r g s i s - t a n c e Zi l a f l e x i o n a t t e i n t l a v a l e u r de 2 0 MPa.

A b s t r a c t - Wall t i l e compositions obtained by r a p i d porous' s i n g l e f i r i n g a r e s t u d i e d using a chamotte from a Sapnish marly limesto- ne. The body f o r m u l a t i o n s a r e made on b a s i s of t h e corresponding phase diagram. Products having, a s t h e main c r y s t a l i n e phases, a n o r t h i t e and q u a r t z a r e o b t a i n e d .

The v a l u e s of t h e p h y s i c a l and t e c h n o l o g i c a l p r o p e r t i e s a r e i n t h e r e q u i r e d range f o r t h e s e k i n d s of m a t e r i a l s . The bending stGength r e a c h e s v a l u e s up t o 20 MPa.

I - INTRODUCTION

This r e p o r t belongs t o a r e s e a r c h l i n e i n which it i s pretended t o use low c o s t raw m a t e r i a l s i n t h e manufacture of ceramic m a t e r i a l s by f a s t f i r i n g .

Here i s used a marly limestone from an importand d e p o s i t l o c a t e d a t t h e province of V a l l a d o l i d ( S p a i n ) .

I n o r d e r t o have an i d e a about t h e use of he r e l a t e d m a t e r i a l , someear- l y t e s t s were made which r e s u l t s were p o s i t i v e / I / . T h e s t u d y o f t h e geo- l o g i c a l formation t o which t h e samples h e r e i n used belong h a s a l s o b e e n made / 2 / .

Nowadays, t h e i n t r o d u c t i o n of a chamotte e n r i c h e d i n a n o r t h i t e , o b t a i n - ed a s from t h e mentioned marly limestone, i n bodies f o r w a l l t i l e s ma- de by porous f a s t s i n g l e f i r i n g i s s t u d i e d .

I1 - MATERIALS AND METHODS

The chamotte used i n t h i s work i s obtained by c a l c i n a t i o n a t 1 0 5 0 ° ~ f r o m a mix of marly limestone and an i l l i t i c - k a o l i n i t i c c l a y . The chemical composition of a l l raw m a t e r i a l s used a r e shown i n Table I.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1986183

C1-550 JOURNAL DE PHYSIQUE

With the related raw materials two bodies are prepared, in which the chamotte being studied plays a role, and a third one, without it,which serves as a term of comparison. The composition of those bodies can be seen in Table 11.

Table I. - Chemical analysis of the materials

The firing ranges are determined and 1080 and 1120°c are chosen as fi- ring temperatures. The firings are made in an intermitent kiln. The heating rate was kept at about 2 8 " ~ / m i n and 6min soacking periodatthe peak temperature was allowed ineach case.

Oxide Weight %

SiO,

~e 2 0 3

Ti0 A1

3

MgO CaO Na , 0 K 2 0

Iqn it ion loss TOTAL

The physicoc'lemical methodsused are the following:

-X-ray powder diffraction ( X R D ) . The quantitative analysis is made by the Chang method /3/, using CaF, as internal standard.

-scann%ng electron microscopy (SEM) with energy-dispersive X-ray spec- trometer (EDAX ) .

The expansion coefficients have been determined on a Lindseis L75unit, the watera,bsorpt%on acaordingtothe UNE 7.061 specification, the appa- rent porosity as a product of the water absorption and the bulk densi- ty and the linear shrinkage was manually determined.

Material

The bending strenght was measured with a Netzch 401 instrument andthe moisture expansion according to the ASTM-C370-56 specification.

Chamotte 48.40

1.50 0.95 28.50 3.40 14.74

1.93 0.46

-

99.88

The addmited ranges for the physical properties here studied are the fo- llowing: water absorption: 14-19%; apparent porosity: 28-34%; bending strength: 15-20 MPa and moisture expansion: up to 1%.

Table 11. - Composition of experimental mixes.

Biscuit body 64.60

1.52 0.06 13.40

5.20 11.90 0.40 1.42

-

99.50

I11 - RESULTS AND DISCUSSION

To make the study of the firing products on the basisofthecorrespond- Hyplast

clay 63.00

0.90 1.50 24.00 0.40 0.20 0.40 2.30 6.80 99.50

Mix

L M N

Sibelco .quartz

97.95 0.06 0.06 1 .I4 0.03 0.01 0.15 0.34 0.14 99.88

Compositions, Weight ( % )

CaC0 3

T-50 0.22 0.02

-

0.20

-

55.26

- -

43.40 99.10

Chamotte 20 10 -

Biscuit body

10 15 5

CaC0 T-50

-

5 15 Hyplast

clay 5 0 50 55

Sibelco quartz

2 0

2 0

2 5

MgO usually forms solid solution with CaO so that the percentage of both oxides are added and considered to be CaO. As it can be seen in Fig. 1 / 5 / , the compositions studied here are situated on the crysta- llization primary field of silica and in the silica-pseudowollastoni- te-anorthite tie traingle. At the firing temperatures such phaseswou&d

SiO

1723-

F i g . I . - T i e t r i a n g l e f r o m t h e S i 0 2 - A Z 2 0 3 - C a 0 p h a s e s d i a g r a m / 4 / . L o c a t i o n o f t h e b o d y c o m p o s i t i o n s .

coexist in the compositions here studied.

The results here obtained are in agreement with these predictions as it can be seen in Table 111.

Table 111. - Constitution and fired properties of bodies.

Firing

tempera- Phase % . ^Apparent Firing Bending ~ i x l O ' Moistu-

'

porpsity shrinka- strenght 25-300 re ex- - Y t u r e o c Qu=tz

% ge % (MPa) OC prnsi.cn Y o 1080 41 25 Tr 2 32 32.2 1.6 13.3 62 1.50 L

1120 41 24 Tr 1 33 30.0 2.8 20.1 68 0.80

C1-552 JOURNAL DE PHYSIQUE

When t h e s e samples a r e o b s e r v e d by SEM F i g . 2 ) , b i g p r i s m a t i c q u a r t z and s m a l l a n o r t h i t e c r y s t a l s c a n be s e e n . I n agreement w i t h p r e v i o u s r e s u l t s o b t a i n e d c r y s t a l s s h a p e s go from s p h e r o i d a l forms (arrow 2 , F i g . 2 ) which c o r r e s p o n d s t o an i n c i p i e n t c r y s t a l l i z a t i o n s t e p of t h e compound u n t i l p r i s m a t i c one (arrow 2, F i g . 2 ) , which b e l o n g s t o more developed c r y s t a l s . According t o t h e EDAX r e s u l t s , and a l s o i n a g r e e - ment w i t h t h e remarks made i n p r e v i o u s s t u d i e s /6/, t h e s i l i c o n , a l u - minium and c a l c i u m c o n t e n t s , o f t h e i n d i v i d u a l c r y s t a l s a r e v a r i a b l e and sometimes s e n s i b l y d e v i a t e s from t h o s e of s t o i c h i o m e t r i c a n o r t h i t e . The g l a s s y phase c a n o n l y b e s e e n a s a background which b i n d s t h e c r y s - t a l l i n e p h a s e s .

On t h e T a b l e I11 t h e p h y s i c a l p r o p e r t i e s of b o d i e s h e r e o b t a i n e d a r e shown. A s it c a n b e s e e n , t h e p o r o s i t y of t h e b o d i e s d e c r e a s e s and t h e f i r i n g s h r i n k a g e i n c r e a s e s w i t h t h e increaseofthechamotteproportion.

T h i s c o u l d be due t o a d e c r e a s e i n t h e CaC03 c o n t e n t , which l e a d t o a lower s h r i n k a g e and t o a h i g h e r p o r o s i t y b e c a u s e o f CO, r e l e a s e . Never- t h e l e s s , t h e v a l u e s o f t h e s e p r o p e r t i e s a r e m a i n t a i n e d , a t t h e t w o t e s t - ed t e m p e r a t u r e s , c l e a r l y w i t h i n t h e admited v a l u e s . T h e b e n d i n g s t r e n g t h l a r g e l y f u l f i l l s t h e r e q u e r i m e n t s f o r t h i s k i n d s o f p r o d u c t s . I t i s o u r o p i n i o n t h a t t h e i n c r e a s e o f t h e bending s t r e n g t h w i t h t h e i n c r e a s e o f t e m p e r a t u r e , i s mainly a t t r i b u t a b l e t o t h e m i c r o s t r u c t u r a l improvement.

I n t h e c o m p o s i t i o n s w i t h chamotte, t h e improvement i s s l i g h t l y l e s s , p r o b a b l y b e c a u s e of t h e lower c a l c i u m c o n t e n t . I t i s a well-known f a c t t h a t a l k a l i n e - e a r t h i o n s improve t h e mechanical s t r e n g t h i n t h e c e r a - mic m a t e r i a l s .

The v a l u e s of m o i s t u r e e x p a n s i o n a r e a d e q u a t e d , mainly i n t h e p r o d u c t s f i r e d a t 1120°C. The p o r e s i z e i n c r e a s e c o u l d b e t h e r e a s o n o f t h e low- er m o i s t u r e e x p a n s i o n w i t h t h e t e m p e r a t u r e t h a t would l e a d t o a s m a l l - e r s p e c i f i c s u r f a c e a r e a and t h i s , i n t u r n , would l e a d t o a d e c r e a s e i n m o i s t u r e .

On t h e o t h e r hand i t i s o b s e r v e d t h a t a s t h e CaO i n c r e a s e s ( l o w e r c o n t e n t o f chamotte) t h e m o i s t u r e e x p a n s i o n a t 1120°C d e c r e a s e s . T h i s f a c t might b e mainly due t o t h e r e a c t i o n o f t h e a l - k a l i n e - e a r t h i o n s w i t h t h e s i l i c a a n d t h e alumina which d i m i n i s h e s t h e de- t r i m e n t a l e f f e c t of t h e s e o x i d e s .

Fig. 2.- S E M i m a g e of body L, 1120°C.

I V - CONCLUSIONS

The r e s u l t s h e r e o b t a i n e d a r e i n agreement w i t h t h e p r e d i c t i o n s made on t h e b a s i s of t h e Ca0-A1203-Si0, diagram.

The f i r e d c o m p o s i t i o n s a r e made of s i l i c a a s a primary p h a s e , i n pro- p o r t i o n s o f 39-41 % and a n o r t h i t e a s secondary p h a s e , w i t h a c o n t e n t of 24-25 %.

The o b s e r v a t i o n s made by SEM and EDAX a l l o w t o o b s e r v e a s fundamental

A1 and Ca of the individual crystals, sometimes sensibly deviates from these stoichiometric anorthite.

The water absorption, the firing shrinkage and the moisture expansion are maintained in the required range for wall tiles; the dilatometric behaviour is good and the bending strength accomplish the performance, with values of 20 MPa or larger.

From the above results, the low-cost raw materials, such as those deve- loped from marly limestones, quite common in Spain, would be suitable for industrial manufacturing of ceramics by porous fast single firing.

ACKNOWLEDGEMENT: T h e a u t h o r w i s h t o e x p r e s s t h e i r t h a n k s t o D r s . P i l a r PENA CASTRO and A n g e l CABALLERO CUESTA f o r t h e i r o r i e n t a t i o n s a b o u t pha- s e d i a g r a m s .

REFERENCES

/I/ Gonzdlez Pefia J.Ma, Sandoval del Rio F. and Alvarez-Estrada D., Ceramic Powders. Edit. Vincencini, Elsevier, Amsterdam (1983)61.

/2/ Gonzdlez Pefia J.Ma, Sandoval del Rio F., Barba Martin-Sonseca F.

and Garcia Rodriguez J.J.,Petrological and Min. Acta. En prensa.

/3/ Chung F.H., J. App. Crystall. 12 (1974) 519.

/4/ Elvin E.M., Robbins C.R. and ~ z u r i d i e H.F. Edit.: The Amer. Ceram Soc. Inc. (1964) 219.

/5/ Lach V., Ceramurgia Intern. 4 (1978) 28.

/6/ Coma-Diaz C., Gonzdlez PeAa J.Ma and Alvarez-Estrada D., Ceramur-

gia Intern. 5 (1980) 771.